chzdev export/prepare-for-import/import bombs out on import in python3.6

chzdev export/prepare-for-import/import bombs out on import in python3.6

like so:

Apr 16 14:05:49 ubuntu-server curtin_log.1663[1766]: Running command ['chzdev', '--quiet', '--persistent', '--no-root-update', '--base', '/etc=/target/etc', '--import', '-'] with allowed return codes [0] (capture=True)
Apr 16 14:05:49 ubuntu-server curtin_log.1663[1766]: finish: cmd-install/stage-curthooks/builtin/cmd-curthooks/installing-kernel: FAIL: installing kernel
Apr 16 14:05:49 ubuntu-server curtin_event.1663[2372]: finish: cmd-install/stage-curthooks/builtin/cmd-curthooks/installing-kernel: FAIL: installing kernel
Apr 16 14:05:49 ubuntu-server curtin_event.1663[2372]: finish: cmd-install/stage-curthooks/builtin/cmd-curthooks: FAIL: curtin command curthooks
Apr 16 14:05:49 ubuntu-server curtin_log.1663[1766]: finish: cmd-install/stage-curthooks/builtin/cmd-curthooks: FAIL: curtin command curthooks
Apr 16 14:05:49 ubuntu-server curtin_log.1663[1766]: Traceback (most recent call last):
Apr 16 14:05:49 ubuntu-server curtin_log.1663[1766]: File "/snap/subiquity/876/lib/python3.6/site-packages/curtin/commands/main.py", line 202, in main
Apr 16 14:05:49 ubuntu-server curtin_log.1663[1766]: ret = args.func(args)
Apr 16 14:05:49 ubuntu-server curtin_log.1663[1766]: File "/snap/subiquity/876/lib/python3.6/site-packages/curtin/commands/curthooks.py", line 1410, in curthooks
Apr 16 14:05:49 ubuntu-server curtin_log.1663[1766]: builtin_curthooks(cfg, target, state)
Apr 16 14:05:49 ubuntu-server curtin_log.1663[1766]: File "/snap/subiquity/876/lib/python3.6/site-packages/curtin/commands/curthooks.py", line 1281, in builtin_curthooks
Apr 16 14:05:49 ubuntu-server curtin_log.1663[1766]: chzdev_persist_active_online(cfg, target)
Apr 16 14:05:49 ubuntu-server curtin_log.1663[1766]: File "/snap/subiquity/876/lib/python3.6/site-packages/curtin/commands/curthooks.py", line 163, in chzdev_persist_active_online
Apr 16 14:05:49 ubuntu-server curtin_log.1663[1766]: persistent=True, noroot=True, base={'/etc': target_etc})
Apr 16 14:05:49 ubuntu-server curtin_log.1663[1766]: File "/snap/subiquity/876/lib/python3.6/site-packages/curtin/commands/curthooks.py", line 210, in chzdev_import
Apr 16 14:05:49 ubuntu-server curtin_log.1663[1766]: return util.subp(cmd, data=data, capture=True)
Apr 16 14:05:49 ubuntu-server curtin_log.1663[1766]: File "/snap/subiquity/876/lib/python3.6/site-packages/curtin/util.py", line 275, in subp
Apr 16 14:05:49 ubuntu-server curtin_log.1663[1766]: return _subp(*args, **kwargs)
Apr 16 14:05:49 ubuntu-server curtin_log.1663[1766]: File "/snap/subiquity/876/lib/python3.6/site-packages/curtin/util.py", line 112, in _subp
Apr 16 14:05:49 ubuntu-server curtin_log.1663[1766]: (out, err) = sp.communicate(data)
Apr 16 14:05:49 ubuntu-server curtin_log.1663[1766]: File "/snap/subiquity/876/usr/lib/python3.6/subprocess.py", line 843, in communicate
Apr 16 14:05:49 ubuntu-server curtin_log.1663[1766]: stdout, stderr = self._communicate(input, endtime, timeout)
Apr 16 14:05:49 ubuntu-server curtin_log.1663[1766]: File "/snap/subiquity/876/usr/lib/python3.6/subprocess.py", line 1499, in _communicate
Apr 16 14:05:49 ubuntu-server curtin_log.1663[1766]: input_view = memoryview(self._input)
Apr 16 14:05:49 ubuntu-server curtin_log.1663[1766]: TypeError: memoryview: a bytes-like object is required, not 'str'
Apr 16 14:05:49 ubuntu-server curtin_log.1663[1766]: memoryview: a bytes-like object is required, not 'str'
Apr 16 14:05:50 ubuntu-server curtin_log.1663[1766]: builtin command failed

http://paste.ubuntu.com/p/KKdr9GFKg5/